Systems and methods for regulating fluid flow for internal cooling and lubrication of electric machines

ABSTRACT

Systems and methods are provided for cooling and lubrication of high power density electric machines with an enhanced fluid injection system. Multiple fluid flow passages are within the electric machine, which include a bearing fluid flow pathway and a rotor fluid flow pathway. The bearing fluid flow pathway comprises a passage which directs fluid to contact a bearing for lubrication and cooling. The rotor fluid flow pathway comprises a passage which directs fluid along the rotatable shaft toward the rotor and stator for cooling. A fluid flow passage may lead to a junction, and may split between the bearing fluid flow pathway and the rotor fluid flow pathway. Additionally, a fluid flow metering device at the junction between the bearing fluid flow pathway and the rotor fluid flow pathway, may determine the relative amount of fluid that flows to the bearing and that flows toward the rotor and stator.

CROSS-REFERENCE

This application is a continuation application of Ser. No. 12/958,321filed Dec. 1, 2010, which is a continuation-in-part application of Ser.No. 12/868,712, filed Aug. 25, 2010, which is incorporated herein byreference in its entirety and to which application we claim priorityunder 35 USC §120.

BACKGROUND OF THE INVENTION

Electric machines have power limitations due to the overheating ofinternal components. In conventional systems, electric machines areoften cooled via exterior cooling. For example, heat sinks may beprovided on the external surface of an electric machine to assist withcooling. In some examples, fluid may flow through an outside enclosureof an electric machine or over an external surface of the machine. See,e.g., U.S. Pat. No. 7,550,882; U.S. Pat. No. 5,939,808; U.S. Pat. No.5,670,838; and U.S. Pat. No. 4,700,092, which are hereby incorporated byreference in their entirety. In some instances, fluid may be providedwithin an electric machine to assist with cooling, but may be containedwithin the machine. See, e.g., U.S. Pat. No. 4,644,202; and U.S. Pat.No. 7,352,090, which are hereby incorporated by reference in theirentirety.

With improved cooling and lubrication of internal components, it ispossible to design an electric machine to produce high power in a muchmore compact and lower weight package as compared to traditional machinedesigns. The improved cooling and lubrication facilitates increasing theoperating current and speed of the machine, which translates directlyinto higher torque, higher power, and consequently higher power density.

Thus, a need exists for improved electric machine systems and methods,which may utilize fluid that may flow internally through an electricmachine for cooling and lubrication.

SUMMARY OF THE INVENTION

The invention provides systems and methods for cooling and lubricationof high power density electric machines with an enhanced fluid injectionsystem. Various aspects of the invention described herein may be appliedto any of the particular applications set forth below or for any othertypes of electric machines. The invention may be applied as a standalonesystem or method, or as part of an integrated system, such as in avehicle. It shall be understood that different aspects of the inventioncan be appreciated individually, collectively, or in combination witheach other.

An aspect of the invention may be directed to an electric machinecomprising a rotor fixed to a rotatable shaft and supported by means ofone or more bearings, a stator stationary in relation to the rotatablerotor and shaft with a gap between the rotor and the stator, a housingsurrounding all or part of the machine, and a fluid distributionmanifold with at least one inlet and a plurality of distributionopenings leading to a plurality of fluid flow passages within themachine in fluid communication with at least one outlet. In someembodiments, the plurality of fluid flow passages may include a statorfluid flow pathway between the stator and the housing, a rotor fluidflow pathway along the rotatable shaft toward the rotor and stator, anda bearing fluid flow pathway contacting at least one bearing. A statorfluid flow pathway may comprise one or more fluid flow passages whichmay allow a fluid to directly contact an outside surface of the stator.One or more grooves or other surface features may form the passagesbetween an outside surface of the stator and an inside surface of thehousing. In some embodiments, one or more fluid flow passages may be influid communication with an exhaust sump which is in fluid communicationwith at least one outlet. The exhaust sump may be configured such thatfluid exiting the fluid flow passages may be collected within the sumpprior to exiting the electric machine through the outlet. In someembodiments, the exhaust sump may function as a heat exchanger, therebyproviding an opportunity to cool the fluid within the sump.

Another aspect of the invention may provide an electric machinecomprising a rotor fixed to a rotatable shaft and supported by means ofone or more bearings, a stator stationary in relation to the rotatablerotor and shaft with a gap between the rotor and the stator, and atleast one fluid flow passage leading to a fluid injector nozzle, whichmay direct fluid along the rotatable shaft toward the rotor and stator.In some embodiments, the fluid injector nozzle and/or the rotatableshaft may include features that may incorporate centrifugal pumping toaid the flow and distribution of the fluid. The electric machine mayalso include a fluid flow passage leading to a junction, wherein thefluid flow pathway may split to contact a bearing and also contact therotor. Additionally, the electric machine may include a metering devicebetween the bearing and the fluid flow pathway leading to the rotor,wherein the metering device is configured to determine the relativeamount of fluid that flows to the bearing and fluid that flows to therotor. In some embodiments, the metering device may be removable,replaceable and/or adjustable, such that the machine may be operatedwithout a metering device, the metering device may be replaced withdifferent metering devices of different configurations, or the meteringdevice may be adjusted, thereby altering the relative amount of fluidthat flows to the bearing and fluid that flows to the rotor.Alternatively, in other embodiments, the fluid flow pathway may notsplit between the bearing and the rotor, but instead, the fluid may bedirected to first contact the bearing, flow through the bearing, andthen subsequently flow to contact the rotor.

A method for cooling an electric machine may be provided in accordancewith another aspect of the invention. The method may include providing arotor fixed to a rotatable shaft, providing a stator stationary inrelation to the rotatable rotor and shaft with a gap between the rotorand the stator, and providing a housing surrounding all or part of themachine. The method may also include directing a fluid to flow throughone or more passages between the stator and the housing, which mayprovide the opportunity to directly contact the stator and the rotorwith the fluid and transfer heat from the stator and the rotor to thefluid, thereby cooling the stator and the rotor.

An additional aspect of the invention may be directed to a system forcooling an electric machine. The system may include an electric machinein fluid communication with a pump, and a heat exchanger in fluidcommunication with the electric machine and the pump. The electricmachine may have a fluid-sealed enclosure with at least one inlet and atleast one outlet, one or more fluid flow passages in fluid communicationwith an inlet and an outlet, and a pressure equalization device that maymaintain the pressure within the machine within a predetermined range.In some embodiments, the machine may also include a device to determinethe level of fluid within the machine. Additionally, in conjunction withthe fluid-sealed enclosure, some embodiments may utilize electricallyconductive material to comprise the contact seals around the rotatingshaft of an electric machine, which may counteract the negative effectsof circulating electric currents generated by homopolar flux paths thatmay exist in electric machines.

Other goals and advantages of the invention will be further appreciatedand understood when considered in conjunction with the followingdescription and accompanying drawings. While the following descriptionmay contain specific details describing particular embodiments of theinvention, this should not be construed as limitations to the scope ofthe invention but rather as an exemplification of preferableembodiments. For each aspect of the invention, many variations arepossible as suggested herein that are known to those of ordinary skillin the art. A variety of changes and modifications can be made withinthe scope of the invention without departing from the spirit thereof.

INCORPORATION BY REFERENCE

All publications, patents, and patent applications mentioned in thisspecification are herein incorporated by reference to the same extent asif each individual publication, patent, or patent application wasspecifically and individually indicated to be incorporated by reference.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of the invention are set forth with particularity inthe appended claims. A better understanding of the features andadvantages of the present invention will be obtained by reference to thefollowing detailed description that sets forth illustrative embodiments,in which the principles of the invention are utilized, and theaccompanying drawings of which:

FIG. 1 shows an electric machine in accordance with an embodiment of theinvention.

FIG. 1A shows a conceptual illustration of an electric machine withfluid flow in accordance with an embodiment of the invention.

FIG. 1B shows a conceptual illustration of a fluid distribution manifoldfor an electric machine in accordance with an embodiment of theinvention.

FIG. 1C shows an example diagram of fluid flow paths that may beprovided within an electric machine.

FIG. 1D shows an alternate example diagram of fluid flow paths that maybe provided within an electric machine.

FIG. 1E shows an alternate example diagram of fluid flow paths that maybe provided within an electric machine.

FIG. 2 shows a bearing fluid flow pathway in accordance with anembodiment of the invention.

FIG. 2A shows magnified views of a bearing fluid flow pathway andbearing assembly in accordance with an embodiment of the invention.

FIG. 3 shows a rotor fluid flow pathway in accordance with an embodimentof the invention.

FIG. 4 shows a conceptual illustration of a system that may be used tocirculate fluid through an electric machine.

FIG. 5 shows a machine shaft in accordance with an embodiment of theinvention.

FIG. 6 shows a fluid-sealed machine enclosure in accordance with anembodiment of the invention.

FIG. 7 shows an exploded view of an electric machine in accordance withan embodiment of the invention.

FIG. 8 shows a conceptual illustration of conductive shaft seals of anelectric machine, as well as homopolar flux paths.

DETAILED DESCRIPTION OF THE INVENTION

While preferable embodiments of the invention have been shown anddescribed herein, it will be obvious to those skilled in the art thatsuch embodiments are provided by way of example only. Numerousvariations, changes, and substitutions will now occur to those skilledin the art without departing from the invention. It should be understoodthat various alternatives to the embodiments of the invention describedherein may be employed in practicing the invention.

I. Fluid Injection System Description

FIG. 1 shows an electric machine in accordance with an embodiment of theinvention. In some embodiments of the invention, the electric machinemay be a motor, such as a three-phase AC induction motor. Alternatively,the electric machine may be any sort of motor, generator, or any sort ofmachine that may require some form of electrical and mechanicalconnection.

The electric machine may also be any machine that may be fluid-cooled orthat may have any sort of fluid in its interior. In some embodiments,the machine may have fluid for cooling and/or lubrication. The fluidwithin the electric machine may be flowing or may be substantiallystationary. In some embodiments, the fluid within the electric machinemay circulate through the electric machine and may come from a sourceexternal to the electric machine. In some embodiments, the machine maybe fluid-sealed or partially fluid-sealed.

The electric machine may be utilized in a system. For example, theelectric machine may be used in a vehicle, such as an automobile,motorcycle, truck, van, bus, or other type of passenger, commercial, orindustrial vehicle, train or other type of railed vehicle, watercraft,aircraft, or any other type of vehicle, or other type of commercial orindustrial machinery or equipment. The electric machine thatincorporates the fluid injection system in accordance with an embodimentof the invention may be particularly useful for applications incontained, controlled, or harsh environments where no localized coolingof the exterior or interior of the machine is possible, and/or a sealedmachine enclosure may be required.

The electric machine may operate at high current levels and highrotational speeds, and may produce much higher power than conventionalmotors of the same size and weight. The fluid injection system may makethis power density possible by allowing for direct cooling of theinternal heat sources, as well as lubrication of the high speedbearings.

FIG. 1A shows a conceptual illustration of an electric machine withfluid flow in accordance with an embodiment of the invention. A fluidfrom an external source may enter an electric machine. The fluid mayenter the machine via one or more inlets. Fluid from within the electricmachine may exit the electric machine. The fluid may exit the machinevia one or more outlets. In some embodiments, the fluid may be providedfrom a fluid source and may exit the machine, such that new fluid isconstantly being used to replenish the fluid within the electricmachine. In other embodiments, fluid may circulate, such that at leastsome, or all, of the fluid exiting the electric machine is cycled toenter the same electric machine. Thus, a fluid injection system may beapplied to the electric machine.

In some embodiments, new fluid may be continually entering the electricmachine and/or old fluid may be continually exiting the electricmachine. In other embodiments, the fluid may be supplied intermittentlyor in batches into the electric machine such that new fluid may be addedand/or old fluid removed, and then after a period of time, more newfluid may be added and/or old fluid removed. New fluid may be added atsubstantially the same rate that old fluid is removed, or new fluid maybe added and/or old fluid removed at different and varying rates. Newfluid and/or old fluid may be added and removed respectively at desiredrates to provide a desired degree of cooling and/or lubrication. In someinstances, it may be desired to increase the rate of fluid flow toincrease cooling and/or lubrication of the electric machine, or todecrease the rate of fluid flow to decrease cooling and/or lubricationof the electric machine.

In other embodiments, the fluid may be contained within the electricmachine and may circulate within the electric machine. In someembodiments, the fluid may be contained within specific parts of theelectric machine, while in other parts, the fluid may flow freelybetween various parts of the electric machine. Any components, features,characteristics, or steps for various fluid-cooled electric machinesknown in the art may be utilized. See, e.g., U.S. Patent Publication No.2006/0066159; U.S. Patent Publication No. 2004/0113500; U.S. Pat. No.5,181,837; U.S. Pat. No. 5,997,261; U.S. Pat. No. 6,355,995; U.S. Pat.No. 5,578,879, which are hereby incorporated by reference in theirentirety.

The cooling and/or lubricating fluid may be any fluid known in the art.A fluid may include a liquid or gaseous fluid. In some embodiments, thecooling and/or lubricating fluid may be a gas, such as air; or a liquid,such as water, oil, or a type of liquid dielectric fluid; or a vapor ormist of any such fluids; or any other type of fluid. Any type of coolantand/or lubricant known in the art may be utilized. For instance, atransmission fluid, such as automatic transmission fluid (ATF) may beused. A fluid may be selected according to desired thermal, electrical,chemical, or flow properties. For example, the fluid may have a specificheat falling within a desired range, or may be a fluid that iselectrically non-conductive with a resistivity above a desired value, ormay be a fluid that is chemically inert or reactive with regard toelements comprising the electric machine, or may be a fluid with a highviscosity or a low viscosity.

In some embodiments, a combination of fluids may be provided within theelectric machine. For example, a cooling and/or lubricating fluid may bea liquid provided within a machine, which also contains a gaseous fluid.In some embodiments, the electric machine may be completely flooded by aliquid fluid, may be partially flooded with a liquid fluid, or may havelow levels of liquid fluid flowing therein.

The fluid supplied to the electric machine may or may not bepressurized. In some instances, the fluid may be pressurized by apositive pressure source, such as a pump or compressor. The positivepressure source may be external to the electric machine (e.g., on theinlet side of the electric machine), or may be part of the electricmachine. In other embodiments, the fluid may be pressurized by anegative pressure source, such as a vacuum. The negative pressure sourcemay be external to the electric machine (e.g., on the outlet side of theelectric machine), or may be part of the electric machine. In someinstances, the pressure source may be integral to the electric machineand may assist with the flow of fluid within the machine. Any pressuredifferential may be created that may assist with fluid flow. In otherembodiments, other forces, such as gravity or forces resulting frommoving parts within the machine, may assist with fluid flow.

All or part of the electric machine may be surrounded by a housing. Themachine housing may include any structure or component that surroundsall or part of the electric machine for the purpose of containment,support, and/or protection, or any other similar functions. A structureor component may function as a machine housing, or may comprise part ofa machine housing, and may additionally perform other unrelatedfunctions. The housing may surround all or part of a machine assembly,or may surround all or part of any of the individual components of themachine, such as a stator or rotor. One or more individual structures orcomponents surrounding all or part of one or more individual componentsof the machine may separately function as machine housings, and may alsocollectively comprise a machine housing. It will be apparent to thoseskilled in the art that the machine housing, referred to herein, mayalso be referenced by other terminology without departing from thedescription provided herein, including machine casing, frame, enclosure,or other similar terms. The machine housing, as referred to herein, maycollectively include any and all individual structures and/or components(e.g., a machine endbell) that may perform the function of containment,support, and/or protection, or any other similar functions, for theelectric machine or any of the individual components of the electricmachine. In some embodiments, all or part of the machine housing may befluid-sealed.

The electric machine may utilize high power electrical connections.Reliable high power connections may require low-resistance electricalcontact with acceptable current density. Typical maximum currentdensities in copper DC power connections may be on the order of 2.2×10⁶A/m². This may typically limit the temperature rise of the connection tounder 30° C. in ambient temperatures over 40° C. See e.g., ANSIC37.20C-1974, IEEE standard 27-1974. In copper three-phase AC powerconnections, maximum peak current densities of 7×10⁶ A/m² havetraditionally been used in electric machines reliably. In someembodiments of the invention, fluid cooling may be introduced to one ormore connector surfaces, which may enhance the connection reliabilityand which may make it possible to exceed the 7×10⁶ A/m² value.

FIG. 1 shows an embodiment of the invention supplying a fluid intovarious passages within an electric machine. The fluid may or may not bepressurized. The fluid may enter the machine through an inlet port 41 ofa fluid distribution manifold 42 and may be distributed to passages atlocations 1, 2, and 3. These passages may direct the fluid to one ormore bearings 7 at location 8, to one or more injector nozzles 9 thatsurround a machine shaft 11 at location 10, and into one or morecavities between a housing 4 and a stator assembly 5 at location 6.Thus, the manifold may distribute fluid to a bearing fluid flow pathway,a rotor fluid flow pathway, and a stator fluid flow pathwayrespectively.

In some embodiments, the passages at locations 1, 2, and 3 may beoriented near the top of the machine, or in other embodiments, thesepassages may be oriented near the bottom of the machine or may beoriented anywhere on any side of the machine. In some instances, thepassages at locations 1, 2, and 3 may each be oriented on substantiallythe same side or in similar positions around the machine, and in otherinstances, the passages may each be individually oriented at anyposition around the machine. In other embodiments, any number ofpassages may be located at any position around the machine.

The fluid entering the passages at locations 1, 2, and 3 may be splitinto multiple paths within the machine. One path may direct some of thefluid to flow through the bearings 7, which may lubricate and cool thebearings (i.e., a bearing fluid flow pathway), and may split to alsodirect some the fluid to flow through the gap 10 between the injectornozzle 9 and the machine shaft 11 toward the rotor and stator, where thefluid may cool the rotor and stator (i.e., a rotor fluid flow pathway).The fluid that has been split to flow through a bearing fluid flowpathway and a rotor fluid flow pathway may complete each pathrespectively by flowing through the main internal cavity 37 of themachine housing 4 to an exhaust passage 20 and into an exhaust sump 22.Note that these paths may be repeated at two locations 1, 3 at each endof the machine. Thus, in some embodiments, two or more bearing fluidflow pathways and two or more rotor fluid flow pathways may be providedwithin the machine.

Another path may direct the fluid to flow around and/or along the statorassembly 5, between the housing 4 and the outer surface of the statorlaminations 5 at location 6, where the fluid may cool the stator and mayalso flow out from the stator to cool the rotor (i.e., a stator fluidflow pathway). Thus, in some embodiments, the same fluid may flowthrough a stator fluid flow pathway to contact and cool both the statorand the rotor. In some embodiments, the fluid may be directedcircumferentially or perimetrically around the stator assembly. Thefluid may alternatively or additionally be directed along the length ofthe stator assembly. In some instances, the fluid may be directedcircumferentially or perimetrically around the stator assembly, and/oralong the length of the stator assembly, at any desired angle. Theinternal surface of the housing 4 may have one or more circumferentialor perimetrical grooves at location 6, which may form one or morecavities between the outside surface of the stator assembly 5 and theinside surface of the housing 4. The fluid may flow through one or moreof these cavities to cool the stator 5 and then, in some embodiments,the fluid may flow through one or more exhaust passages 21 into anexhaust sump 22. Alternatively or additionally, the internal surface ofthe housing 4 and/or the outside surface of the stator assembly 5 mayhave one or more grooves or other surface features, which may form oneor more passages along the length of the stator assembly, between theoutside surface of the stator assembly and the inside surface of thehousing. The fluid may flow through one or more of these passages tocool the stator 5 and then, in some embodiments, the fluid may exit oneor more of the passages at the edge of the stator laminations. The fluidmay then flow to contact and cool the stator end turns and the rotor endrings, and may then flow through the main internal cavity 37 of themachine housing to one or more exhaust passages 20 and into the exhaustsump 22. In some embodiments, one stator fluid flow pathway may beprovided within the machine. Alternatively, in other embodiments, two ormore stator fluid flow pathways may be provided.

In some embodiments, fluid that has flowed through a stator fluid flowpathway, fluid that has flowed through a rotor fluid flow pathway, andfluid that has flowed through a bearing fluid flow pathway may allcollect together in the exhaust sump 22, where the fluid may exit themachine through an outlet port 46. Preferably, the same fluid may beused for all of the fluid flow paths within the machine. In otherembodiments, different fluids or combinations thereof may be used fordifferent fluid flow paths.

A. Fluid Distribution Manifold

As previously described, FIG. 1 shows an inlet port 41 and a fluiddistribution manifold 42 through which fluid may enter an electricmachine in accordance with an embodiment of the invention. In someembodiments, the inlet port may be oriented to be on a side of theelectric machine. In other embodiments, the inlet port may be orientedto be from the top of the electric machine, or the bottom of theelectric machine. In some instances, the inlet port may be oriented suchthat the fluid flows horizontally to the fluid distribution manifold.Alternatively, the inlet port may be oriented vertically, or at an anglewhich may include but is not limited to a 10 degree angle, 15 degreeangle, 30 degree angle, 45 degree angle, 60 degree angle, 75 degreeangle, or 80 degree angle. In some instances, one, two, three, or moreinlet ports may be provided, where each inlet port may have anyconfiguration, location, or orientation, as described. Each inlet portmay connect to the same fluid distribution manifold or may alternativelyconnect to different manifolds which may or may not be in fluidcommunication with one another. Each inlet port may accept the samefluid or a different type of fluid. An inlet port may be provided on anypart of the housing of the electric machine, with or without the use ofa manifold. In some embodiments, the manifold may be provided as a partof and/or contained within the housing of the electric machine. In otherembodiments, the manifold may be provided as a separate part andattached to the housing of the electric machine. Still in otherembodiments, the manifold may be provided such that a portion of themanifold is provided as a separate part attached to the machine andanother portion of the manifold is provided as a part of and/orcontained within the machine.

FIG. 1B shows a conceptual illustration of a fluid distribution manifoldfor an electric machine in accordance with an embodiment of theinvention. As shown, fluid may enter the manifold from one or moreinlets. The fluid distribution manifold may have one or moredistribution openings that may lead to one or more fluid flow passageswithin the machine. In one example, three distribution openings and/orfluid flow passages may be provided I, IIA, IIB. In other embodiments,any number of distribution openings and/or fluid flow passages may beprovided, which may include one, two, three, four, five, six, seven,eight, nine, or ten or more distribution openings and/or fluid flowpassages.

In some instances, the same number of distribution openings and/or fluidflow passages may be provided. Alternatively, different numbers ofdistribution openings and/or fluid flow passages may be provided. Forexample, multiple fluid flow passages may branch off from a singledistribution opening or from other fluid flow passages.

The fluid distribution manifold may have any shape or orientation. Insome instances, the manifold may have an elongated or flattened shape.For example, the manifold may have a flattened circular, square,rectangular, triangular, hexagonal, octagonal, or any other shape. Insome instances, the manifold may be oriented horizontally, such that asmallest dimension extends in a vertical direction. Alternatively, themanifold may be oriented vertically, such that a smallest dimensionextends in a horizontal direction. In other embodiments, the manifoldmay be oriented at an angle.

The distribution openings may be located anywhere along the manifold.For example, the distribution openings may be located on a bottomsurface of the manifold. This may enable gravity to assist with causingfluid to flow through the openings. In other embodiments, thedistribution openings may be located on a side or top of the manifold.

FIG. 1 shows that, in an embodiment of the invention, fluid may enterthe machine through an inlet port 41 of a fluid distribution manifold 42and may be distributed to passages at locations 1, 2, and 3. The fluidflow passages may be formed of channels, enclosed spaces, non-enclosedspaces, flat spaces, tubes, pipes, or any other shape or configuration.As previously discussed, any number of fluid flow passages may beprovided for an electric machine.

FIG. 1C shows an example diagram of fluid flow paths that may providedwithin an electric machine. A first fluid flow path I may be a statorfluid flow pathway. The stator fluid flow pathway may be providedbetween a housing of the electric machine and a stator assembly. In oneembodiment, one stator fluid flow pathway may be provided.Alternatively, multiple stator fluid flow pathways may be providedwithin the electric machine. In some embodiments, a stator fluid flowpathway may cause fluid to flow over a substantially curved surface of asubstantially cylindrical electric machine, around the axis of rotationof the machine. For example, if a cylindrically shaped machine wereprovided on its side, such that the axis of rotation of the rotatablerotor and shaft of the machine were parallel to the ground, fluid mayflow from above the cylindrical machine and downward, around the curvedsurface of the cylinder, such that it flows substantiallycircumferentially around the stator assembly. In other embodiments, theelectric machine need not be substantially cylindrical and, as such, thestator fluid flow pathway may alternatively cause fluid to flow aroundany shaped surface or multiple surfaces, such that fluid may flow aroundthe perimeter of any shape of stator. Alternatively or additionally, inother embodiments, the fluid may flow in any direction or multipledirections around the stator. In some embodiments, a stator fluid flowpathway may cause fluid to flow over the surface of the stator along thelength an electric machine, substantially parallel with the axis ofrotation of the machine. For example, fluid may flow from a passage nearthe center of the stator assembly and may flow outward along the lengthof the stator, such that it flows substantially parallel with the axisof rotation of the rotatable rotor and shaft of the electric machine. Inother embodiments, the stator fluid flow pathway may cause fluid to flowat any angle or direction along or around the stator assembly. Forexample, the fluid may flow at about 5 degrees, about 10 degrees, about15 degrees, about 20 degrees, about 30 degrees, about 45 degrees, about60 degrees, about 75 degrees, or about 90 degrees relative to the axisof rotation.

As also shown in FIG. 1C, additional fluid flow paths may be providedwithin the electric machine. For example, a rotor fluid flow pathwayIIA, IIB and a bearing fluid flow pathway IIIA, IIIB may be provided. Arotor fluid flow pathway may be provided, which may direct fluid tocontact a rotor and a stator assembly. A bearing fluid flow pathway maybe provided, which may cause fluid to contact a bearing assembly. Insome embodiments, one, two, or more rotor fluid flow pathways and/orbearing fluid flow pathways may be provided. In some embodiments, tworotor fluid flow pathways and two bearing fluid flow pathways may beprovided, including one of each on opposite sides of an electricmachine. For example, they may be provided along substantially flat endsof a substantially cylindrical electric machine. Alternatively, anynumber of rotor fluid flow pathways and bearing fluid flow pathways maybe provided around an electric machine. For example, if an electricmachine has a circular cross-sectional shape, multiple rotor fluid flowpathways and multiple bearing fluid flow pathways may be provided aroundvarious points of the circumference of the electric machine. In someembodiments, a rotor fluid flow pathway and a bearing fluid flow pathwaymay originate with the same fluid flow passage IIA+IIIA, IIB+IIIB, andmay branch off into a separate rotor fluid flow pathway IIA, IIB and aseparate bearing fluid flow pathway IIIA, IIIB.

In alternate embodiments of the invention, such as shown by the examplediagram of fluid flow paths in FIG. 1D, the rotor fluid flow pathwayIIA, IIB and the bearing fluid flow pathway IIIA, IIIB need not sharethe same originating fluid flow passage. Instead, the rotor fluid flowpathway IIA, IIB and the bearing fluid flow pathway IIIA, IIIB may haveseparate individual distribution openings from the manifold, leading toseparate individual fluid flow passages.

In other alternate embodiments, such as shown by the example diagram offluid flow paths in FIG. 1E, the rotor fluid flow pathway IIA, IIB andthe bearing fluid flow pathway IIIA, IIIB may originate with the samefluid flow passage IIA+IIIA, IIB+IIIB, and may not branch off into aseparate rotor fluid flow pathway IIA, IIB and a separate bearing fluidflow pathway IIIA, IIIB. Instead, a single fluid flow passage IIA+IIIA,IIB+IIIB may direct fluid to flow in series through a bearing fluid flowpathway IIIA, IIIB and then sequentially through a rotor fluid flowpathway IIA, IIB.

In some embodiments, a stator fluid flow pathway may or may not shareany part of a fluid flow passage with a rotor fluid flow pathway and/ora bearing fluid flow pathway. In accordance with one embodiment, anelectric machine may have five fluid flow paths: one stator fluid flowpathway, two rotor fluid flow pathways, and two bearing fluid flowpathways.

The electric machine may include one or more fluid distributionmanifolds. Each manifold may have a similar configuration or varyingconfigurations. In some instances, each manifold may providedistribution openings to each of the fluid flow pathways. Alternatively,various manifolds may provide distribution openings to different fluidflow pathways.

B. Stator Fluid Flow Pathway

In some embodiments, fluid may flow through a stator fluid flow pathway.FIG. 1 shows a cooling fluid path that may route fluid to flow betweenan electric machine housing 4 and a stator assembly 5, in accordancewith an embodiment of the invention. The fluid may enter one or morefluid flow passages at location 2 and may flow through one or morecavities 6 formed by a circumferential or perimetrical groove on theinternal surface of the housing 4. Alternatively or additionally, fluidmay flow through one or more passages along the length of the statorformed by grooves or other features on the internal surface of thehousing 4 and/or the outside surface of the stator assembly 5. Thus, insome embodiments, fluid may flow through one or more passages around thecircumference or perimeter of the stator, and/or flow though one or morepassages along the length of the stator, in any direction or multipledirections. In some instances, fluid may exit one or more of thepassages along the length of the stator at the edge of the statorlaminations, allowing fluid to flow over and/or through the stator endturns and onto the rotor end rings. Thus, the stator fluid flow pathwaymay comprise one or more fluid flow passages which may allow the fluidto directly contact the outside surface of the stator assembly 5, thestator end turns, and the rotor end rings. It will be apparent to thoseskilled in the art that the stator laminations, stator end turns, androtor end rings, referred to herein, may include any other similarstructures or components in any type of electric machine withoutdeparting from the invention described herein.

Direct contact between the cooling fluid and the stator laminations,stator end turns, and rotor end rings may enhance the thermal transferfrom the stator and rotor heat sources to the cooling fluid. This fluidflow path may be enabled by a sealed construction of the machineenclosure. Thus, in some embodiments, a housing for the electric machinemay be fluid-sealed, or the portion of the housing in contact with thecooling fluid may be fluid-sealed, however, the machine may not need tobe fluid-sealed in some embodiments.

In some embodiments, the fluid entering the fluid flow passage atlocation 2 may flow through the cavity 6 around the entire circumferenceor perimeter of the stator assembly 5, and then may exit the cavitythrough an exhaust passage 21 and into an exhaust sump 22, where thefluid may exit the machine through a fluid outlet port 46. In otherembodiments, the fluid entering the fluid flow passage at location 2 mayflow through the cavity 6 around part of the circumference or perimeterof the stator assembly 5. Alternatively or additionally, the fluidentering the fluid flow passage at location 2 may flow through one ormore passages along the length of the stator assembly 5, and then, insome embodiments, the fluid may exit one or more of the passages at theedge of the stator laminations. The fluid exiting the one or morepassages at the edge of the stator laminations may then flow to contactthe stator end turns and the rotor end rings, and may then flow throughthe main internal cavity 37 of the machine housing to an exhaust passage20 and into the exhaust sump 22, where the fluid may exit the machinethrough a fluid outlet port 46. In some embodiments, the fluid maycontact a stator end turn and/or rotor end ring in one or more locationsat one end of the machine or at both ends of the machine.

FIG. 7 shows an exploded view of an electric machine in accordance withan embodiment of the invention. A perspective view of a stator assembly5 is provided. Fluid may flow along the exterior surface of the statorassembly 5, around and/or along the central curved region shown. Inother embodiments, the exterior surface of the stator assembly need notbe curved and, as such, fluid may flow around and/or along any shape ofstator surface or multiple stator surfaces. In some embodiments, thefluid may flow downward around the entire circumference of the statorassembly 5 and, and in some instances, be collected by an exhaust sump22, which may be located beneath the stator. In other embodiments, thefluid may flow around part of the circumference of the stator assembly5. In some embodiments, the fluid may flow along the length of thestator assembly 5, and may flow in a direction outward from center ofthe stator toward one or more edges of the stator. In other embodiments,the fluid may flow along the length of the stator from one edge of thestator toward the center and/or from one edge of stator to the otheredge of the stator. In some instances, fluid flowing in a passage towardthe edge of the stator may exit the passage at the edge of the statorlaminations and flow into the main internal cavity of the machine. Afterexiting the passage at the edge of the stator laminations, the fluid mayadditionally flow to contact the stator end turns, and may continue toflow around and/or through the stator end turns to contact the rotor endrings. The fluid may then flow downward through the main internal cavityof the machine housing and, in some instances, be collected by anexhaust sump 22, which may be located beneath the stator and rotor.

In some embodiments, the fluid flow may be confined to a specific regionbetween the stator 5 and a housing 4. In some cases, the fluid flow maybe confined within cavities, channels, chambers, zones, or any otherfluid confining structure. One or multiple confined fluid flow passagesmay be provided. In other embodiments, the fluid may flow freelyanywhere in the space between the stator and the housing. In someembodiments, the fluid may flow in any direction or multiple directionsin any space or combination of spaces between the stator and thehousing. The fluid may flow freely over a wide area and/or may berestricted to one or more specified paths. In some embodiments, thefluid may be directed in a path that may cause the fluid to flow in onedirection, or multiple directions. Additionally, a fluid flow path maychange the direction of the fluid flow at any point and any number oftimes. In some embodiments, the fluid may flow along a continuous path,or may branch off into different paths. Zero, one, two, or more pathsmay branch off from zero, one, two, or more points. Fluid may flow alonga single defined path and/or may flow along multiple paths in parallel.Multiple fluid flow paths may or may not be parallel to one another.

One or more features may be provided on the inside surface of thehousing and/or the outside surface of the stator assembly, which mayform one or more passages configured to direct the fluid flow betweenthe stator and the housing. Additionally or alternatively, these one ormore features may increase the exposed surface area of the outsidesurface of the stator and/or the inside surface housing, which may aidin heat transfer between either or both surfaces and the fluid. In someembodiments, the internal surface of the housing may include one or moregrooves, channels, ridges, protrusions, fins, bumps, indentations,patterns, textured surfaces, or any other surface features. In someinstances, these features may form one or more passages configured todirect the fluid flow around or along the stator surface, between theoutside surface of the stator assembly and the inside surface of thehousing. Additionally or alternatively, these features may increase theexposed internal surface area of the housing, which may increase theamount of surface area of one or more fluid flow passages in contactwith the fluid. This may advantageously allow a greater degree of heattransfer between the fluid and the housing surface. Alternatively, inother embodiments, the internal surface of the housing may be smooth orsubstantially smooth. In some embodiments, the exterior surface of thestator assembly may include one or more grooves, channels, ridges,protrusions, fins, bumps, indentations, patterns, textured surfaces, orany other surface features. In some instances, these features may formone or more passages configured to direct the fluid flow around or alongthe stator surface, between the outside surface of the stator assemblyand the inside surface of the housing. Additionally or alternatively,these features may increase the exposed surface area of the stator,which may increase the amount of surface area of one or more fluid flowpassages in contact with the fluid. This may advantageously allow agreater degree of heat transfer between the stator surface and thefluid. Alternatively, in other embodiments, the stator surface may besmooth or substantially smooth.

In some instances, fluid may flow downward along all or part of thestator fluid flow pathway, and the fluid flow may be driven or assistedby gravity. In other instances, pumps, compressors, or other mechanismsmay be utilized to actively force the fluid to flow in a desired mannerthrough all or part the stator fluid flow pathway. Such forced fluidflow may allow the fluid to travel in any direction around and/or alongthe stator fluid flow pathway, which may include allowing the fluid totravel upwards, downwards, sideways, or at any angle. Thus, the fluidmay flow through the stator fluid flow pathway due to one or more of thefollowing: gravity, positive pressure at the start of the fluid flowpathway or at some point along the fluid flow pathway, negative pressureat the end of the fluid flow pathway or at some point along the fluidflow pathway, or one or more moving parts or other mechanisms which maybe external to the electric machine or an integral part of the electricmachine.

C. Rotor Fluid Flow Pathway

Embodiments for a fluid flow pathway to cool the rotating rotor (orsimilar dynamic component in other types of electric machines, such asan armature) and stationary stator assembly are described in thissection.

FIG. 3 provides a magnified detail of a section of an electric machineand shows a rotor fluid flow pathway in accordance with an embodiment ofthe invention. The fluid may flow from a fluid passage 1 into a cavity45 near a fluid injector nozzle 9, through a gap 10 between the injectornozzle 9 and a machine shaft 11, and then out through a vertical gap 16between the injector nozzle 9 and the face of a rotor 35. A largerdiameter feature at the end of the injector nozzle 9 adjacent to theface of the rotor 35 may cause the fluid to increase in speed as itexits the gap 16 due to the centrifugal force of the rotating rotor 35.Thus, the part of the injector nozzle that forms the vertical elementadjacent to the face of the rotor may also function as a centrifugalpumping disc 34.

Once the fluid is ejected from the gap 16, it may impact the end ring 15of the rotor at the surface 17 and may cool the end ring 15. The rotorend ring 15 may represent the shorting ring for the rotor bars in aninduction machine with a cage style rotor, the end turns in a woundrotor type machine, the end structure of the rotor in a permanent magnettype machine, or any similar structure in any type of electric machine.

The rotor end rings 15, especially on wound or cage type machines, maybe made from a high electrically conductive material. In someembodiments, the end rings may also be made of a high thermallyconductive material. Some examples of such thermally conductivematerials may include, but are not limited to, metals (such as copper,aluminum, brass, silver, gold, iron, steel, lead), diamond, carbon, orany alloy, mixture, or combinations thereof. Cooling the end rings 15with the fluid flow may cause the heat from the center of the rotor tobe removed by thermal conduction to the lower temperature end rings andfluid. In some embodiments, thermally conductive materials or devices(such as heat pipes), which may be either electrically conductive ornon-conductive, may be added to the rotor assembly and may be in thermalcommunication with the rotor structure and/or end rings to improve heattransfer.

Once the fluid is ejected from the end ring 15 by centrifugal force, itmay spin off toward the stator end turns 18, where additional maycooling take place. The stator end turns may be the ends of the windingsof a stator assembly 5, which may consist of a high electrically andthermally conductive material, and thus may effectively conduct heatfrom the center of the stator 5 to the fluid. In some embodiments, thewindings of the stator assembly may be formed of copper, aluminum, orany other high electrically conductive material. In some instances, thewindings of the stator assembly may also be formed of a high thermallyconductive material. In some types of electric machines, the statorassembly may contain permanent magnets rather than windings, such aswith brushed universal motors. In some embodiments, thermally conductivematerials or devices (such as heat pipes), which may be eitherelectrically conductive or non-conductive, may be added to the statorassembly and may be in thermal communication with the stator structureand/or end turns to improve heat transfer.

As shown in FIG. 1, once the fluid impacts the stator end turns 18, itmay flow away from the end turns due to the effect of gravity to anexhaust passage 20 of the main internal cavity 37 of the machine housing4. The machine housing, or the portion of the housing in contact withthe cooling fluid, may be fluid-sealed, which may enable the fluid toflow without leaking from the housing, however, the machine may not needto be fluid-sealed in some embodiments. From the exhaust passage 20, itmay flow into an exhaust sump 22 and exit the machine through a fluidoutlet port 46.

One or more rotor fluid flow pathways may be provided within an electricmachine. For example, as shown in FIG. 1C, two similar fluid flow pathsIIA+IIIA and IIB+IIIB may be provided. These two similar fluid flowpaths may be provided at opposite ends of an electric machine. In otherembodiments, there may be any number of rotor fluid flow pathways andthey may have any location within the electric machine.

As shown in FIG. 3, the fluid may flow from a fluid flow passage 1 to acavity 45. The cavity may be a junction at which some of the fluid maybranch off into a rotor fluid flow pathway and some of the fluid maybranch off into a bearing fluid flow pathway. The cavity may form ajunction with any number of configurations, branching off to any numberof fluid flow pathways. Alternatively, the cavity need not form ajunction, but may direct all of the fluid to flow along a specificpathway.

The fluid may flow from the cavity 45 along a passage between aninjector nozzle 9 and a machine shaft 11 and a face of the rotor 35. Thefluid may flow in a substantially horizontal direction along a firstpart of the rotor fluid flow pathway 10 and may flow in a substantiallyvertical direction along a second part of the rotor fluid flow pathway16. In other embodiments, these fluid flow passages may have anyorientation, whether they be angled (e.g., 5 degrees, 15 degrees, 30degrees, 45 degrees, 60 degrees, 75 degrees, 85 degrees), or horizontal,or vertical. The fluid flow pathway sections may also be substantiallystraight, or may be bent, or curved. In some instances, the first partof the fluid flow pathway 10 may transition to the second part of thefluid flow pathway 16 through an intermediate segment that may be angledor curved. In other instances, the first part of the fluid flow pathwaymay directly transition to the second part of the fluid flow pathwaywith no intermediate segment. In other embodiments, the first and secondparts of the fluid flow pathway may be merged into one passage.

The fluid may or may not require pressure to flow along a fluid flowpassage between the injector nozzle and machine shaft. The pressure maybe caused by a positive pressure source, such as a pump, a negativepressure source, such as a vacuum, or any other pressure differentialgenerating device. Pressure may be caused by an external source or asource integral to the machine. In some instances, gravity may cause orcontribute to the pressure.

In some embodiments, the gap between the injector nozzle 9 and themachine shaft 11 or face of the rotor 35 may vary. For example, in someinstances, the gap between the injector nozzle and face of the rotor maybe greater than the gap between the injector nozzle and machine shaft,or vice versa. In some instances, the gaps may be on the order of 0.5 to1.0 mm, however, the size of the gaps may vary accordingly as a functionof fluid flow and pressure requirements, the type of fluid, and/or thesize of the machine.

The fluid exiting the fluid flow passage 16 may impact the rotor endring 15. In some embodiments, the rotor end ring may be beveled or mayhave any other shape. The rotor end ring may be horizontal or may beangled or curved as desired. This will be discussed in greater detailbelow. As previously described, the fluid may optionally impact thestator end turns 18, and flow away from the end turns. Alternatively,the fluid may impact any other surface provided in the region near thestator and the rotor. The fluid may flow downward due to the effect ofgravity to an exhaust passage 20. The fluid may flow down any surfacenear or integral to the stator and the rotor. In some embodiments, theremay be channels or surface features on any of the surfaces that mayassist with directing the fluid downwards and/or to a desired location.Alternatively, the surfaces may be substantially smooth.

As shown in FIG. 3, other components that may be located near a rotorfluid flow pathway may include a housing 4 for the electric machine. Thecavity 45 may be located near a bearing 7, which may be held in place bya bearing outer race 31 and a bearing inner race 32. This will bediscussed in further detail below. Furthermore, a shaft seal 13 may beprovided.

D. Bearing Fluid Flow Pathway

A bearing fluid flow pathway may also be provided in accordance with anembodiment of the invention. The fluid pathway to the bearings may allowfluid to flow through the bearings for lubrication and cooling. This mayfacilitate higher operating speeds, longer continuous operation, highermachine durability and reliability, and longer machine life. Theincreased operating speeds may be a key enabler to producing higherpower and achieving higher power density from an electric machine.

FIG. 2A provides magnified views of the bearing fluid flow pathway andbearing assembly in accordance with an embodiment of the invention. Thefluid may enter into a cavity 45 on one side of a bearing 7, then mayflow through a metering device 29, through gaps in the bearing assembly,and into a cavity 12 on the other side of the bearing 7 between thebearing and a shaft seal 13.

The bearing 7 may be supported by an outer race 31 and an inner race 32,which may comprise a bearing assembly. The fluid may flow between thebearing and one or more of the races. Alternatively, some or all of thefluid may flow around the bearing without going between the bearing andthe races.

FIG. 2 illustrates that a drain passage 14 may allow the fluid to exitthe cavity 12 and flow out into the main internal cavity of the machinehousing 4. FIG. 1 shows how the fluid may flow through the main internalcavity 37 of the machine housing 4 to an exhaust passage 20. From theexhaust passage 20, the fluid may be directed to an exhaust sump 22,where it may exit the machine through a fluid outlet port 46. Themachine housing, or the portion of the housing in contact with thecooling fluid, may be fluid-sealed, which may enable to the fluid toflow without leaking from the housing, however, the machine may not needto be fluid-sealed in some embodiments.

As shown in FIG. 8, a contact seal 13 may be provided around a shaft 11of an electric machine and may prevent the fluid from exiting themachine through the interface between the rotating shaft 11 and amachine housing 4. In some embodiments, the shaft seal 13 may becomprised of electrically conductive material, which may complete anelectrical path between the rotor 35 and the stator 5. In traditionalmachines, bearings may need to be electrically insulated from themachine housing and the rotor to prevent circulating electric currents43 from flowing through the bearings 7, which may cause prematurebearing failure due to electrical erosion. By using a conductive seal13, the currents 43 may flow through the conductive seal 13 instead ofthe bearings 7, which may serve to prevent premature bearing failure.Shaft seals 13 may be provided at one or both ends of the rotating shaft11, or at any location where the shaft extends through the machinehousing 4. Thus, one or more shaft seals may be electrically conductive,however, the shaft seals may not need to be electrically conductive insome embodiments. The conductive seals will be discussed in greaterdetail below.

One or more bearing fluid flow pathways may be provided within anelectric machine. For example, in some embodiments, two bearing fluidflow pathways may be provided at opposite ends of an electric machine.In some instances, the bearing fluid flow pathways may branch off fromone or more fluid passages that may be provided within an electricmachine. For example, as shown in FIG. 1C, two similar fluid flow pathsIIA+IIIA and IIB+IIIB may be provided. These two similar fluid flowpaths may be provided at opposite ends of an electric machine. Thebearing fluid flow pathways IIIA, IIIB may branch off from these twofluid flow paths. In other embodiments, any number of bearing fluid flowpathways may branch off from each fluid flow path, or the bearing fluidflow pathways IIIA, IIIB need not branch off from another fluid flowpath, but may be directly connected to a fluid distribution manifold,such as shown in FIG. 1D. In other embodiments, there may be any numberof bearing fluid flow pathways and they may have any location within theelectric machine.

1. Method of Splitting Fluid Flow for Bearing Lubrication and Cooling

FIG. 2A shows magnified views of a bearing fluid flow pathway inaccordance with an embodiment of the invention. In a bearing fluid flowpathway of the fluid injection system, the fluid may be directed into acavity 45, where the fluid may be split between a bearing 7 and a fluidinjector nozzle 9. Thus, the cavity 45 may form a junction where thefluid may split in two or more directions. In some embodiments, thefluid flow may split into a bearing fluid flow pathway, which may directsome of the fluid through a bearing 7 to lubricate and cool the bearing,and into a rotor fluid flow pathway, which may also direct some of thefluid through a gap 10 between an injector nozzle 9 and a machine shaft11 toward the rotor and stator.

In some embodiments, the injector nozzle 9 may or may not require fluidpressure for the fluid injection system to work properly, but it may bedesired to regulate or meter the relative amount of fluid flow to thebearing 7, versus the amount of fluid flow through the pathway leadingto the rotor and stator. This may be accomplished by the use of a fluidflow metering device 29, captured between the injector nozzle 9 and thebearing assembly, which may comprise one or more bearings 7, a bearinginner race 32, and a bearing outer race 31. The bearing assembly 7, 31,32 and metering device 29 may be secured by the injector nozzle 9, whichmay serve both to capture the metering device 29 and secure it in place,as well as clamp the bearing assembly 7, 31, 32 in place. Clamping thebearing assembly in place may keep the bearing assembly from shifting orspinning as the machine housing 4 temperature increases, due todifferences in thermal expansion properties between the bearing assemblymaterials and the housing material.

Any of the components mentioned above may be formed of any materials ofdesired properties. For example, the bearings may be steel bearings thatmay be relatively less costly to manufacture than some other types ofbearings. While steel may be preferable for rolling element bearings,other metals, plastics, glass, and/or ceramics, or any combinationthereof may also be used. The housing may be formed of, but not limitedto, aluminum, steel, iron, copper, brass, silver, gold, lead or anyother metal, or other materials such as plastics, glass, ceramics, orany alloy, mixture, or combination thereof.

The use of a high thermal conductivity material for the housing 4, suchas aluminum, may create a thermal expansion mismatch with regard to thematerial of the bearing 7, the bearing inner race 32, and/or the bearingouter race 31, which, for example, may be formed of steel. The housingbore 30, in which the bearing assembly 7, 31, 32 is seated, may expandin size faster with increased temperature than the bearing assembly,which may allow the bearing assembly 7, 31, 32 to shift or spin in thehousing 4. Because of this effect, it may be desired to clamp thebearing assembly 7, 31, 32 in place. This may be accomplished with theinjector nozzle 9, which, in addition to its fluid distributionfunction, may also serve as a bearing clamp, eliminating the need forextra hardware to perform each function.

To control the fluid flow through the bearing 7, the metering device 29may be clamped against a bearing outer race 31. In one embodiment, asmall gap 33 between the metering device 29 and the bearing inner race32 may be used to manage the rate of fluid flow through the bearing 7,so as to maintain fluid pressure into the injector nozzle 9, and yetprovide enough fluid to lubricate and cool the bearing 7.

In some embodiments, the metering device 29 may have holes, channels, orpassages, or be constructed of perforated, porous, permeable, orsemi-permeable material, which may enable fluid to flow from one side ofthe metering device to the other through the metering device. In suchsituations, a gap 33 may or may not be provided for the metering device29. Alternatively, the metering device 29 may be solid and may not haveholes, channels, or passages within. The metering device 29 may beformed of a material that may be impermeable, semi-permeable, orpermeable with respect to the fluid that may flow therethrough. In someembodiments, the metering device may be a plate, or may have any othershape or configuration.

In some embodiments, the metering device 29 may be removable,replaceable, and/or adjustable, such that the machine may be operatedwithout a metering device, the metering device may be replaced withdifferent metering devices of different sizes and/or configurations, orthe metering device may be adjusted, thereby altering the relativeamount of fluid that flows to the bearing 7 and fluid that flows to theinjector nozzle 9. Thus, the use of the metering device 29 may allow forinterchangeable devices, each with a different size or configuration offluid passage to match the desired fluid flow rate or accommodate theuse of different types of fluids.

For example, small gaps 33 or holes may be used for gas fluids, andlarger gaps 33 or holes may be used for higher viscosity liquids. Thesize and/or configuration of the metering device may also be adjusted todetermine the relative amount of fluid that flows to the bearing 7 andfluid that flows to the injector nozzle 9. For example, if it is desiredthat relatively more of the fluid flow into the bearing fluid flowpathway, the size or configuration of the metering device may beadjusted such that the size of the gap 33 or the holes may be increased,which may allow more fluid to flow through the metering device into thebearing fluid flow pathway.

In some embodiments, a metering device 29 may be adjustable. Forexample, the size of the metering device may be adjustable, which mayvary the size of a gap 33. Alternatively, the number or sizes of holes,channels, or paths through the metering device may be variable. One ormore valves may be provided. Other adjustable features that mayaccommodate different fluids and/or flow rates may be provided.

The metering device 29 may have a substantially vertical configuration.In other embodiments, the metering device may be angled. The meteringdevice may be angled at a desired amount in order to allow a desiredrate or proportion of fluid to flow into the bearing fluid flow pathway.

The use of a metering device 29 may advantageously allow the sameelectric machine to be used with different types of fluids. The meteringdevices may be interchanged and/or adjustable features may be controlledto accommodate different fluids, but other changes may not need to bemade to the electric machine. This may contrast with traditionalelectric machine designs, which may require entirely differentconfigurations, and/or may need to be replaced entirely, to accommodatedifferent types of fluids.

2. Alternate Method of Fluid Flow for Bearing Lubrication/Cooling andRotor Cooling

In another embodiment of the invention, an alternate method of fluidflow for a bearing fluid flow pathway and a rotor fluid flow pathway maybe provided, as compared to the method previously described. As shown inFIG. 1E, the rotor fluid flow pathway IIA, IIB and bearing fluid flowpathway IIIA, IIIB may originate with the same fluid flow passageIIA+IIIA, IIB+IIIB, and may not branch off into a separate rotor fluidflow pathway IIA, IIB and a separate bearing fluid flow pathway IIIA,IIIB. Instead, a single fluid flow passage IIA+IIIA, IIB+IIIB may directfluid to flow in series through a bearing fluid flow pathway IIIA, IIIBand then sequentially through a rotor fluid flow pathway IIA, IIB. Thismethod presents a unique fluid flow path that may allow fluid to flowthrough one or more bearings for lubrication and cooling, and then maysubsequently allow fluid to flow through a rotor fluid flow pathway forcooling of a rotor and a stator assembly. This method may beparticularly applicable when larger bearings are used, although it mayoptionally be used with bearings of any size.

FIG. 2 shows an example of a bearing fluid flow pathway in accordancewith one embodiment of the invention. In an alternate embodiment, fluidmay be injected first into a cavity located at 12, rather than into acavity located at 45, as shown in FIG. 2A. Fluid may first flow into acavity located at 12 via one or more fluid flow passages that may beconnected to a fluid distribution manifold. The fluid flow passage mayor may not also branch off into a rotor fluid flow pathway prior toreaching the cavity 12. In preferable embodiments, the fluid flowpassage does not branch off separately to a rotor fluid flow pathway. Adrain passage 14 and/or metering device 29 may or may not be eliminatedin this method. If the drain passage is eliminated, the fluid from thebearing flow pathway may all be directed through the bearing 7.

This method of fluid flow may be similar to the method describedpreviously, with the exception that a fluid passage 1 may enter thecavity located at 12 on the same side of the bearing as the shaft seal,and the drain passage 14 may be eliminated as well. Fluid may flow fromthe cavity located at 12, through a bearing 7, and into the cavitylocated at 45. The fluid may then continue through a gap 10 between aninjector nozzle 9 and a machine shaft 11, and then flow out through avertical gap 16 between the injector nozzle 9 and the face of a rotor35, as shown in FIG. 3, to contact a rotor end ring 15 and stator endturns 18 as described previously. Thus, with this alternate method offluid flow for bearing lubrication/cooling and rotor cooling, the fluidflow path may not split between the bearing 7 and injector nozzle 9, butinstead, the fluid may flow in series directly through the bearing 7 andthen into the gap 10 between the injector nozzle 9 and machine shaft 11.

In this alternate method, fluid may flow through a bearing fluid flowpathway, and then sequentially flow through a rotor fluid flow pathway.This may enable the bearing and the rotor to be cooled and/or lubricatedin sequence, rather than in parallel as provided in the previous method.Thus, a particular fluid may first contact one or more bearings, flowthrough the bearing or bearings, and then flow through a rotor fluidflow pathway in any of the embodiments or variations described. This maybe contrasted with methods where fluid flow paths may branch off, suchthat fluid may flow through a bearing fluid flow pathway and a rotorfluid flow pathways in parallel, with separate fluid contacting thebearing and the rotor.

II. Centrifugal Pumping of Fluid from Injector Nozzle

FIG. 3 shows a rotor fluid flow pathway in accordance with an embodimentof the invention. A centrifugal pumping disk 34 may be provided adjacentto a surface of a rotor 35. The centrifugal pumping disk may beintegrally formed from an injector nozzle 9. Alternatively, thecentrifugal pumping disk may be separate from the injector nozzle. Thepumping disk and the rotor may form a gap 16 which may be part of therotor fluid flow pathway.

For the rotor fluid flow pathway of the fluid injection system, the useof a larger diameter parallel centrifugal pumping disk 34 on the outputof the injector nozzle 9, which may be stationary with respect to therotating rotor 35, may cause the fluid to flow in a radial directionthrough the gap 16 between the disk 34 and the face of the rotor 35 andmay increase fluid velocity. As the fluid velocity increases, thepressure of the fluid may drop, and the disk 34 may act as a centrifugalpump to aid the flow and distribution of the fluid. This method mayadvantageously incorporate centrifugal pumping as an integral part ofthe machine design, which may increase or enhance the fluid flow withinthe machine, and/or may eliminate or reduce the requirement for externalpumping of fluid in some embodiments of the invention.

From Bernoulli's equation:

P+½ρV ² +ρgh=K,

where

-   -   P is pressure,    -   ρ is density,    -   V is fluid velocity,    -   g is gravity,    -   h is height change,    -   K is a constant.

Assuming constant temperature, the fluid velocity, V, increases due tothe rotating action of the rotor, thus causing the fluid pressure, P, todecrease. This pressure drop may allow the injector nozzle to functionas a centrifugal pump.

Increasing the size of the centrifugal pumping disk 34 may increase thepumping effect. The use of a substantially smooth surface on the disk 34may reduce the drag losses on the machine. If greater pumping effectsare required, the addition of vanes on the surface of the rotatingcentrifugal pumping disk 34 may increase the pumping pressure due toadditional changes in fluid velocity, but may require more power fromthe machine to operate. Furthermore, as illustrated in FIG. 5,additional centrifugal pumping force may be achieved by providingfeatures, such as vanes 36, on the machine shaft 11. These vanes may bein the region of a gap 10 between the shaft 11 and the fluid injectornozzle 9, as illustrated in FIG. 3. These vanes 36 may act to pump thefluid through the gap 10. The vanes may be angled to assist withdirecting the fluid in a desired direction. For example, the vanes maybe angled such that fluid flows toward the center of the electricmachine (i.e., through a first gap 10 and then transitioning to a secondgap 16). Alternatively, grooves, ridges, channels, or any other surfacefeatures maybe provided to assist with directing the fluid and affectingthe pumping pressure.

The centrifugal pumping disk 34 may be formed of any material that mayprovide the desired mechanical and/or surface properties to assist withthe pumping effect. As previously mentioned, it may be desirable for thesurface of the centrifugal pumping disk to be substantially smooth. Insome other embodiments, the centrifugal pumping disk may have a texturedsurface, or other surface features such as channels, ridges,indentations, or vanes that may affect the fluid flow through the gap 16adjacent to the disk. The disk surface adjacent to the face of the rotor35 may be oriented vertically, or may have some angle, that may directthe fluid in a desired manner.

Because additional fluid flow may not be required at all times, thismethod of enhancing fluid flow by means of centrifugal pumping mayautomatically enable increasing the fluid flow when additional coolingis needed most. As the rotational speed of the machine increases, thepower of the machine may also increase, and thus, the heat loss from themachine may also increase. The integrated centrifugal pumping method mayproportionally increase the rate of fluid flow with respect to therotational speed of the machine, which may simultaneously increase theheat transfer rate of the cooling system at times of high poweroperation. Thus, as the need for heat transfer within the machineincreases, increased fluid flow and heat transfer may be provided bymeans of the centrifugal pumping method.

III. Method of Enhancing Fluid Flow and Heat Transfer on Rotor End Ring

In traditional machines, rotor end rings of electric machines are oftenmade with fins to circulate air in machine housings and increaseconvection heat transfer.

In a fluid injection cooled machine, the heat transfer mechanism may beby means of conduction and/or convection to the injected fluid. As shownin FIG. 3, the injected fluid may exit a gap 16, spray onto the internaldiameter of a rotor end ring 15, and flow over and around the end ringto spray onto stator end turns 18.

The rotor end ring 15 may be provided at a desired distance from theopening of the gap 16 between a fluid injector nozzle 9 (and/orcentrifugal pumping disk 34) and the face of a rotor 35. For example,the distance between the opening of the gap 16 and the rotor end ring 15may be adjusted accordingly to provide a desired amount of fluid flowand/or to control the direction of fluid flow. Additionally, in someembodiments, the fluid injector nozzle 9 and/or centrifugal pumping disk34 may be configured and/or include features such that the fluid exitingthe gap 16 is directed in a desired manner toward the rotor end ring 15.

To enhance the heat transfer and fluid flow on the rotor end ring, therotor end ring may include one or more features that may increase thesurface area exposed to the fluid that has exited the gap 16 and/or thatmay aid in directing the fluid to flow over the surface of the rotor andthen toward the stator by centrifugal force. In some embodiments, therotor end ring surface may be substantially flat or may include abeveled feature 17. The addition of a beveled feature 17 on the internaldiameter of the end ring 15 may increase the surface area exposed to thecooling fluid. In some embodiments, the rotor end ring surface may besubstantially smooth or may include surface features, such as channels,ridges, protrusions, vanes, indentations, or any other feature, whichmay increase the surface area of the rotor end ring that may be exposedto the fluid and/or which may enhance the flow of the fluid over andaround the end rings. The features may be aligned in a manner that mayencourage fluid flow along the length of the rotor end ring 15 to spraythe fluid toward the stator end turns 18.

A beveled feature 17 may also increase the rate of fluid flow due to thedirection of the centrifugal force, and therefore, may increase the rateof heat transfer from the rotor end ring 15 to the fluid. The additionof the beveled feature 17 on the internal diameter of the end ring mayenhance the fluid flow because the centrifugal force will have an axialvelocity component. This feature may reduce the fluid film thickness andmay increase fluid velocity across the surface of the end ring, thusincreasing the heat transfer rate, while minimizing wind losses in themachine.

The desired degree of beveling may be at any angle N where Nis a numberbetween 0 and 90 relative to horizontal. For example, the beveledfeature may be about 1 degree, 2 degrees, 3 degrees, 5 degrees, 7degrees, 10 degrees, 12 degrees, 15 degrees, 20 degrees, 25 degrees, 30degrees, 35 degrees, 40 degrees, 45 degrees, 50 degrees, 60 degrees, 70degrees or about 80 degrees or more or less.

In some instances, the beveled surface may be substantially smooth.Alternatively, any number of additional surface features may beincorporated that may further increase the surface area exposed to thefluid, that may further enhance the fluid flow rate over the surface ofthe rotor, and/or that may aid in directing the fluid flow over therotor and ring toward the stator.

IV. Sealing Machine Shaft with Electrically Conductive Seals

FIG. 8 shows an illustration of conductive shaft seals of an electricmachine, as well as homopolar flux paths that may exist in electricmachines driven by means of an AC inverter. These flux paths maygenerate circulating electric currents 43 between a rotor 35, a stator5, and a housing 4. If the rotor is not electrically insulated from thestator and/or the housing, these currents may flow through the machinebearings 7, particularly if the bearings are metallic, or otherwiseelectrically conductive.

In some embodiments, the bearings may be metallic rolling elementbearings, such as ball or roller bearings, and the currents 43 may flowthrough the rolling contacts of the bearings. These rolling contacts maybe small surface area contacts, such as point or line contacts, wherehigh current densities may occur and electrical arcing may create pitson the bearing races 31, 32.

Rolling contacts between the bearings and the bearing races may beintermittent contacts as the balls or rollers may be rolling at highspeeds. These intermittent contacts, combined with the high currentdensity, may cause arcing to occur many times per revolution of thebearing, and may ultimately cause destructive pitting on the surfaces ofthe bearing assembly materials. The pitting on the surfaces of thebearing assembly may lead to bearing failures and may substantiallyshorten the life of the machine bearings.

Traditional solutions to this problem include using special electricallyinsulated bearings, such as bearings with ceramic rolling elements, orelectrical insulators on the machine shaft 11, inner bearing race 32, orouter bearing race 31. These solutions may be expensive and/orunreliable.

In accordance with an embodiment of the invention, the machine with aninternal fluid injection system may require a sealing method on themachine shaft 11 to prevent leakage of fluid from the machine. This maybe achieved by using a contact seal 13, which may prevent fluid fromexiting the machine at the interface between the machine shaft 11 andthe housing 14. In some embodiments, the contact seal may contact thehousing and/or the machine shaft. If the contact seal 13 is made from anelectrically conductive material, the seal may also provide anelectrical connection between the machine shaft 11 and the housing 4.

This novel method of sealing may provide an alternate path 43 for thecurrent to flow through the conductive shaft seals 13, and thus, maypresent a solution to the circulating current problem. The seal 13 mayhave a much larger surface area contact than the bearings, andtherefore, the circulating current 43 may mostly flow through the seal13. Thus, when the bearings make intermittent contact with the bearingraces, electrical arcing may not occur between the bearings and theraces, as the seal may provide an alternate path for the circulatingcurrent 43.

In some embodiments, the material for the contact seal may be selectedsuch that it has a high electrical conductivity. In some embodiments,the contact seal may be formed of a material with a greater electricalconductivity than the material selected for the bearing and/or thebearing races. For example, if a contact seal 13 has a first electricalconductivity of E1, and a bearing 7 has a second electrical conductivityof E2, then E1 may be greater than E2. Thus, the circulating electriccurrent 43 may preferably flow through the contact seal 13 rather thanthrough the bearing 7. However, in some embodiments, E1 may not need tobe greater than E2 for the circulating electric current to preferablyflow through the contact seal rather than through the bearing, as theseal may have much greater surface area contact relative to the surfacearea contact of the bearing, which may be substantially a point or linecontact. The larger surface area contact of the seal may cause theeffective electrical conductivity of the seal to be greater than theeffective electrical conductivity of the bearing and/or bearing raceswhen operating in an electric machine.

Some examples of materials that may be used for the contact seal mayinclude, but are not limited to, aluminum, copper, brass, nickel,titanium, graphite, carbon, silver, gold, iron, steel, or any alloy,mixture, or combinations thereof. The contact seal may be plated, clad,or include layers or components of various materials, includingelemental metals. The contact seal may be formed from any plastic orelastomer (such as polytetrafluoroethylene) and may be filled, orpartially filled, with conductive material. The contact seal may beformed of, or may include, an elemental metal, any other conductivematerial, or any combinations thereof.

By using a conductive contact seal 13, circulating electric current 43may be prevented or reduced from flowing across the bearing 7 and mayallow for the use of more cost-effective conventional metallic bearings,without the issue of premature bearing failure due to pitting occurringon the bearing races 31, 32 due to electrical arcing. Thus, by providinga seal that may be used to prevent fluid leakage from the housing, andby using a conductive material for that seal, conventionalcost-effective metallic bearings may be used reliably in an electricmachine.

V. Exhaust Sump as Heat Exchanger

FIG. 1 provides an example of an electric machine in accordance with anembodiment of the invention. The electric machine may include a fluidinjection system, and may provide for various fluid flow paths withinthe machine. The fluid may be used for cooling and/or lubrication of theelectric machine. The fluid temperature may be increased through heattransfer from the heat sources of the machine, after which the fluid maycollect at the base of the machine, where it may be pumped out to anexternal remote heat exchanger, such as shown in FIG. 4.

As shown in FIG. 1, the fluid within the electric machine may flowdownwards and be collected in an exhaust sump 22. Because there may be avolume of fluid collected in the exhaust sump 22, and also may be somedelay in time before the fluid exits the machine, there may be anopportunity to remove heat from the fluid at this location. Thus, theexhaust sump may also function as an integrated local heat exchanger.

FIG. 1 shows an exhaust sump 22 of an electric machine in one embodimentof the invention. The heat removal may be accomplished by applyingcooling fins 23 to the exhaust sump 22, which may provide additionalcooling to the fluid prior to exiting the sump. In some embodiments, oneor more external heat sinks may also be applied to the exterior surfaceof the exhaust sump. Alternatively, cooling fins and/or other featuresintegral to the exhaust sump may cause the exterior of the exhaust sumpto function as a heat sink. The cooling fins and/or heat sinks may haveany configuration that may increase the surface area on the exteriorsurface of the exhaust sump and/or enhance thermal transfer from theexhaust sump. The cooling fins and/or heat sinks may be formed of amaterial with high thermal conductivity.

In some embodiments, heat may dissipate passively from the cooling finsand/or heat sinks In other embodiments, a device, such as a fan, may beused to blow a gas over the surface of the cooling fins and/or heatsinks to aid in active cooling. In other embodiments, another fluid mayflow over the surface of the cooling fins and/or heat sinks, over anyexterior surface of the exhaust sump, or through any part of the exhaustsump, whether that fluid has a gaseous or liquid form. The other fluidmay be actively passed over the cooling surfaces, whether it be with theaid of a fan, pump, compressor, or any other device generating apressure differential, or any other active cooling mechanism. The otherfluid may be channeled as part of a local heat exchanger and/or as partof another remote heat transfer system. Depending on the type of fluids,the exhaust sump may function as a gas-to-gas heat exchanger,liquid-to-gas heat exchanger, gas-to-liquid heat exchanger,liquid-to-liquid heat exchanger, or any other type or configuration ofheat exchanger.

In accordance with some embodiments of the invention, the exhaust sumpmay have an outlet port 46, as shown in FIG. 1. In other embodiments,multiple outlet ports may be provided. Alternatively, no outlet portsmay be provided and the fluid may be recirculated within the electricmachine. The exhaust sump may be shaped to funnel the fluid toward oneor more outlet. For example, the bottom surface of the sump may besloped to allow fluid to drain toward the outlet. The fluid may exit theoutlet, driven by gravitational forces, pressure differentials,centrifugal forces, or any other forces.

Because the exhaust sump 22 may act to collect a volume of cooling fluid(especially if a liquid coolant is used), there may be a time delaybetween the time the fluid enters the sump 22 and the time the fluidexits the sump 22. In some instances, the sump may act a fluidreservoir, such that a volume of fluid may be collected within the sumpprior to exiting the sump. The level of fluid in the system may beadjusted such that a volume of fluid may consistently exist or becollected within the sump. Fluid may enter the sump at any rate and mayexit the sump at any rate, such that fluid may enter and exit the sumpat substantially the same or different rates. In some instances, fluidmay exit the sump continuously, while in other instances, fluid maycollect within the sump for a period of time and then exit at variousrates or intervals. Thus, the fluid that may be collected within theexhaust sump may be cooled prior to exiting the exhaust sump.

In some embodiments, the time that the fluid may be collected within theexhaust sump may be used to pre-cool the fluid prior to being pumped outto the rest of the heat transfer system, such as shown in FIG. 4. FIG. 4shows an electric machine 24 that may include an exhaust sump in fluidcommunication with a recirculation pump 25. The pre-cooling of the fluidwithin the exhaust sump may advantageously reduce the operatingtemperature requirements of a recirculation pump in a fluid circulationsystem for an electric machine. In other embodiments, the fluid may beremoved from the electric machine and need not be recirculated. Still inother embodiments, the fluid may be recirculated within the electricmachine and need not be removed from the machine.

VI. Overall Fluid Circulation System

FIG. 4 shows a conceptual schematic of system that may be used tocirculate fluid through an electric machine 24, in accordance with anembodiment of the invention. An electric machine 24 may be provided suchthat it is in fluid communication with a pump 25. The pump may be influid communication with a one-way check valve 19, which may be in fluidcommunication with a filter 26, which may be in fluid communication witha heat exchanger 27. The heat exchanger 27 may be in fluid communicationwith the electric machine 24 to complete the fluid flow circuit.Alternately, the pump may be in fluid communication with a one-way checkvalve 19, which may be in fluid communication with a heat exchanger 27,which may be in fluid communication with a filter 26. The filter 26 maybe in fluid communication with the electric machine 24 to complete tofluid flow circuit. In other alternate embodiments, the components ofthe fluid circulation system may be arranged in any order in the fluidflow circuit. Furthermore, a plurality of one or more of the componentsmay be included in the circuit, and/or one or more of the components maybe eliminated from the circuit.

In accordance with an embodiment as shown in FIG. 4, a fluid may enteran electric machine 24 through an inlet, and exit the electric machine24 through an outlet. The fluid that has exited the electric machine maypass through a pump 25, which may drive fluid flow. The fluid may passthrough a one-way check valve 19, which may allow fluid to flow throughthe device in only one direction and may prevent fluid from flowing inthe reverse direction and back into the electric machine. The fluid maypass through a filter 26 before passing through a heat exchanger 27. Theheat exchanger 27 may preferably transfer heat from the fluid, such thatthe fluid is at lower temperature when exiting the heat exchanger. Fromthe heat exchanger 27, the fluid may enter the inlet of the electricmachine 24. Thus, the fluid may be recirculated within the system,driven by a recirculation pump. The fluid may be used to cool and/orlubricate the electric machine, and may be heated while in the electricmachine. The fluid may be cooled outside the electric machine via anexternal heat exchanger, and may thus be cooled before re-entering theelectric machine.

The pump 25 may be any type of pump known in the art that may cause adesired amount of fluid to circulate through the system at a desiredrate, or that may comprise any other desired characteristics. Forexample, the pump may be a centrifugal, diaphragm, gear, vane, impeller,flexible liner, injection, piston, progressing cavity, peristaltic, orlobe pump, or any other type or configuration of pump. Furthermore, thepump may be positioned remotely from, attached to, or contained withinthe machine. The pump may be a device that is separate from or integralto the electric machine, and may be powered by any source, which may beseparate from or the same as the machine, and/or the pump may derivepower from the machine.

The external heat exchanger 27 may be a liquid-to-liquid, gas-to-gas, orliquid-to-gas heat exchanger, or any other type of heat exchanger knownin the art. For example, a fluid may enter the heat exchanger and maytransfer heat to another fluid. The other fluid may be a gas or aliquid. A heat exchanger may have any form or configuration known in theart. In some instances, a heat exchanger may have a plate-typeconfiguration. Alternatively, the heat exchanger may have a shell andtube type configuration.

The purpose of the heat exchanger may be to extract heat from themachine cooling fluid, so as to ultimately transfer the heat to theambient air or other fluid. The removal of heat from the machine coolingfluid may provide for lower machine operating temperature, and thus mayimprove machine reliability. Additionally, lower operating temperatureof the machine may result in lower electrical resistance values for thestator and rotor conducting materials. This may effectively reduceresistive losses in the machine, which may translate into improvedmachine efficiency.

A. Recirculation Pump Circuit, with Machine Housing as Thermal ExpansionChamber, Plenum, and Fluid Reservoir

FIG. 4 shows that, in one embodiment of the invention, a recirculationpump 25 may transfer fluid from the fluid outlet of an electric machine24, through a check valve 19, through a filter device 26, through a heatexchanger 27, and then to the fluid inlet of the electric machine 24.The recirculation pump may drive the fluid flow within the system. Insome instances, the recirculation pump may be controlled to vary thespeed of fluid flow. For example, the speed of fluid flow may beincreased, decreased, or maintained by controlling the recirculationpump. Thus, the fluid flow speed may be varied and/or maintained basedon the controllable recirculation pump. The speed of the fluid flow mayaffect the rate of heat transfer provided to the electric machine. Inthis recirculating heat transfer circuit, the machine housing 4, asshown in FIG. 1, may act as a thermal expansion chamber, plenum, and/orreservoir for the recirculating fluid.

FIG. 1 shows an electric machine in accordance with an embodiment of theinvention. Electric machines containing fluid may typically beconfigured either as an open circuit (open to the atmosphere) or as aclosed circuit (closed to the atmosphere) in a fluid circulation system.The closed circuit machine configuration typically may require aseparate expansion chamber to prevent fluid leakage from the system dueto thermal expansion of the circulating fluid.

A partially fluid filled machine, in accordance with an embodiment ofthe invention, may allow the machine housing 4 to function as a thermalexpansion chamber and the main internal cavity 37 of the machine housing4 to act as a plenum, with one or more pressure equalization featuresadded to the machine. The pressure equalization features may include apressure equalization device 28, as described in greater detail below.This method may allow for the use of a closed circuit fluid circulationsystem, without the need for external expansion chambers or fluidreservoirs. When pressure increases or decreases within the machinehousing 4, the use of a pressure equalization device may allow pressureequalization within the machine and fluid circulation system, and maythus aid in preventing fluid leakage from the system.

As the system temperature rises, the fluid within the machine mayincrease in temperature and expand, causing an increase in pressurewithin the machine. To equalize the pressure within the machine, themachine housing may include a pressure equalization device 28, such as avalve, piston, sintered metal vent, or expandable bladder. The pressureequalization device may allow the machine housing to function as athermal expansion chamber and plenum, equalizing the pressure within thefluid-sealed machine with the external ambient pressure, as thetemperature of the fluid within the machine changes. The pressureequalization may keep the pressure within the machine housing within apredetermined range. In some embodiments, the predetermined range may beany pressure less than or equal to and/or greater than or equal to oneor more threshold pressures. In some instances, a threshold pressure maybe an ambient pressure. Thus, a pressure equalization device 28 may beprovided on the electric machine 24 to allow for pressure equalization,while still maintaining the integrity of the fluid-sealed enclosure. Oneor more pressure equalization devices may be located, preferably,anywhere on the machine housing that properly facilitates this pressureequalization.

A partially fluid filled machine, in accordance with an embodiment ofthe invention, may allow the machine housing to function as the fluidreservoir. In some embodiments, the electric machine may have one ormore fluid level devices 48 that may allow a user or inspector todetermine the level of fluid inside the machine housing. The fluid leveldevice may be any type of physical, mechanical, electrical, electronic,optical, pneumatic, ultrasonic, or radio frequency device, or anycombination thereof, or any other type or configuration of sensing,measuring, or indicating device known in the art or later developed,such that the device may provide feedback to the user or inspectorregarding the level of fluid within the machine.

In some embodiments, the electric machine may have one or moretransparent windows that may provide visual feedback regarding the levelof fluid within the machine. The window may enable a user or inspectorto view within the electric machine and determine the fluid levelinside. The window may be formed of a transparent material and may stillallow the electric machine housing to maintain a fluid-sealed machineenclosure. The window may be any shape or size and may enable a user orinspector to determine the fluid level, or range of fluid levels, withinthe machine. One or more windows may be placed on one or more sides ofthe electric machine at a location consistent with determining thedesired fluid level within the machine housing. One or more windows mayalso be placed on or near the exhaust sump to view the fluid levelwithin the exhaust sump, which may also function as part of the fluidreservoir.

B. Fluid-Sealed Machine Enclosure

FIG. 6 shows a fluid-sealed machine enclosure in accordance with anembodiment of the invention. To implement the fluid injection system, amachine housing 4 may be a sealed enclosure, in which the housingfeatures are sealed at all joints and junctions to prevent leakage ofinternal fluids from the machine. Use of a fluid-sealed construction maytypically not be needed for conventional machines, but may be animportant feature for the fluid injected machine design.

Seals may be introduced between a removable end bell 38 and housing 4,between dielectric insulators 39 for power contacts and the endbell 38,between power contacts 40 and the dielectric insulators 39, and betweena rotating machine shaft 11 and the endbell 38 and housing 4.

The mounting hardware for fluid injector nozzles 9 may be accessed andinstalled from the outside of the machine, so therefore seals may alsobe implemented at locations 47 between the injector nozzles and machinehousing 4 and endbell 38, to inhibit fluid from flowing to the injectornozzle mounting hardware locations and to prevent fluid leakage throughthe hardware interfaces. The fluid injector mounting hardware may beinstalled from the outside of the machine to prevent damage to therotating components within the machine in the case of a fastener comingloose. In this embodiment of the design, if a fastener disengages, itmay always be on the outside of the machine, away from the internalrotating components.

The sealed housing 4 may accommodate thermal expansion of the internalfluid, due to temperature changes. A method of pressure equalization maybe used to prevent pressure inside of the machine from becomingexcessive due to fluid thermal expansion. The sealed housing design mayincorporate a pressure equalization device 28, which may allow forpressure equalization and may prevent fluid leakage from the machine dueto increased pressure. The lower pressure may be less demanding on theshaft seal 13 and may allow for the use of a cost-effective, lowersealing pressure, standard shaft seal.

To simplify the interface to the fluid flow circuit, the sealed housingmay feature a fluid distribution manifold 42 and exhaust sump 22, asshown in FIG. 1, where a single fluid inlet 41 to the machine and asingle fluid outlet 46 from the machine may be achieved. Alternatively,any number of fluid inlets or outlets may be provided. The manifold 42may allow for a single fluid inlet connection, with an internal plenum,which may distribute the fluid to one or more fluid flow passages within the machine. Similarly, the exhaust sump 22 may be used to collectthe fluid exiting the fluid flow passages within the machine throughexhaust passages 20 and 21. The exhaust sump 22 may provide for thecollection of a volume of fluid within the sump, prior to exiting themachine through a single outlet port 46.

It should be understood from the foregoing that, while particularimplementations have been illustrated and described, variousmodifications can be made thereto and are contemplated herein. It isalso not intended that the invention be limited by the specific examplesprovided within the specification. While the invention has beendescribed with reference to the aforementioned specification, thedescriptions and illustrations of the preferable embodiments herein arenot meant to be construed in a limiting sense. Furthermore, it shall beunderstood that all aspects of the invention are not limited to thespecific depictions, configurations or relative proportions set forthherein which depend upon a variety of conditions and variables. Variousmodifications in form and detail of the embodiments of the inventionwill be apparent to a person skilled in the art. It is thereforecontemplated that the invention shall also cover any such modifications,variations and equivalents.

1. An electric machine comprising: a rotor fixed to a rotatable shaft and supported by means of one or more bearings; a stator stationary in relation to the rotatable rotor and shaft with a gap between the rotor and the stator; one or more fluid flow passages within the machine, wherein at least one fluid flow passage leads to a junction wherein the fluid flow splits into a bearing fluid flow pathway to contact the one or more bearings and into a rotor fluid flow pathway toward the rotor and stator; and a fluid flow metering device at the junction between the bearing fluid flow pathway and the rotor fluid flow pathway, wherein the fluid flow metering device is configured to determine the relative amount of fluid that flows to contact the one or more bearings and fluid that flows toward the rotor and stator.
 2. The electric machine of claim 1 wherein the fluid flow metering device is removable, such that if the machine is operated without the fluid flow metering device, the relative amount of fluid that flows to contact the one or more bearings and fluid that flows toward the rotor and stator is altered.
 3. The electric machine of claim 1 wherein the fluid flow metering device is replaceable, such that if the fluid flow metering device is replaced by one or more different metering devices of different sizes and/or configurations, the relative amount of fluid that flows to contact the one or more bearings and fluid that flows toward the rotor and stator is altered.
 4. The electric machine of claim 1 wherein the fluid flow metering device is adjustable, such that if the configuration or position of the fluid flow metering device is adjusted, the relative amount of fluid that flows to contact the one or more bearings and fluid that flows toward the rotor and stator is altered.
 5. The electric machine of claim 1 wherein the rotor fluid flow pathway comprises a fluid injector nozzle, wherein the fluid injector nozzle surrounds the rotatable shaft and a gap between the fluid injector nozzle and the rotatable shaft is formed, and wherein fluid is directed to flow along the rotatable shaft through the gap between the fluid injector nozzle and the rotatable shaft toward the rotor and stator.
 6. The electric machine of claim 5 wherein the fluid flow metering device is captured between the fluid injector nozzle and the one or more bearings, and wherein the fluid flow metering device and the one or more bearings are secured in place by the fluid injector nozzle.
 7. The electric machine of claim 1 wherein the fluid flow metering device comprises a plate which forms a gap between the one or more bearings and the rotor fluid flow pathway, such that the size of the gap determines the relative amount of fluid that flows to contact the one or more bearings and fluid that flows toward the rotor and stator.
 8. A method for regulating fluid flow for internal cooling and lubrication of an electric machine comprising: providing a rotor fixed to a rotatable shaft and supported by means of one or more bearings; providing a stator stationary in relation to the rotatable rotor and shaft with a gap between the rotor and the stator; providing one or more fluid flow passages within the machine, wherein the one or more fluid flow passages comprise: one or more bearing fluid flow pathways comprising one or more passages which direct fluid to contact the one or more bearings for lubrication and cooling of the one or more bearings; one or more rotor fluid flow pathways comprising one or more passages which direct fluid along the rotatable shaft toward the rotor and stator for cooling of the rotor and stator; and an introductory fluid flow passage leading to a junction, wherein the fluid flow splits between the bearing fluid flow pathway and the rotor fluid flow pathway; and providing a fluid flow metering device at the junction between the bearing fluid flow pathway and the rotor fluid flow pathway, wherein the fluid flow metering device is configured to determine the relative amount of fluid that flows to contact the one or more the bearings and fluid that flows toward the rotor and stator.
 9. The method of claim 8 further comprising operating the machine without the fluid flow metering device, thereby altering the relative amount of fluid that flows to contact the one or more bearings and fluid that flows toward the rotor and stator.
 10. The method of claim 8 further comprising replacing the fluid flow metering device by one or more different metering devices of different sizes and/or configurations, thereby altering the relative amount of fluid that flows to contact the one or more bearings and fluid that flows toward the rotor and stator.
 11. The method of claim 8 further comprising adjusting the configuration or position of the fluid flow metering device, thereby altering the relative amount of fluid that flows to contact the one or more bearings and fluid that flows toward the rotor and stator.
 12. The method of claim 8 wherein the one or more rotor fluid flow pathways comprise a fluid injector nozzle, wherein the fluid injector nozzle surrounds the rotatable shaft and a gap between the fluid injector nozzle and the rotatable shaft is formed, and wherein fluid is directed to flow along the rotatable shaft through the gap between the fluid injector nozzle and the rotatable shaft toward the rotor and stator.
 13. The method of claim 12 wherein the fluid flow metering device is captured between the fluid injector nozzle and the one or more bearings, and wherein the fluid flow metering device and the one or more bearings are secured in place by the fluid injector nozzle.
 14. The method of claim 8 wherein the fluid flow metering device comprises a plate which forms a gap between the one or more bearings and the rotor fluid flow pathway, such that the size of the gap determines the relative amount of fluid that flows to contact the one or more bearings and fluid that flows toward the rotor and stator. 